Since pointing out relevant related questions in comments seems to be positively seen by the community. I think it's a useful addition to the ones that are automatically linked.
Would it be appropriate to encourage pointing out related questions with a badge?
As an example, you would get points when:
- you are the first to link the question
- your comment gets upvoted n times
- the link get m hits
To be clear, I'm not talking about duplicates which should be pointed out for moderation, but related questions.